linux-kernel - Re: The difference of request dir between AS and Deadline I/O scheduler?

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Date:	Tue, 03 Mar 2009 15:58:23 +1100
From:	Aaron Carroll <aaronc@....unsw.edu.au>
To:	谢纲 <xiegang112@...il.com>
CC:	linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>
Subject: Re: The difference of request dir between AS and Deadline I/O 	scheduler?

谢纲 wrote:
> On Tue, Mar 3, 2009 at 12:21 PM, Aaron Carroll <aaronc@....unsw.edu.au> wrote:
>> � wrote:
>>> Hi,
>>>
>>> I'm little confused about the defination of request dir in AS and
>>> Deadline I/O scheduler.
>>> In AS, the request dir is defined by wheher it's sync:
>>>
>>> data_dir = rq_is_sync(rq);
>>>
>>> But in Deadline, the requests are grouped by read and write.
>>>
>>> Why is there the difference since AS is an extension of Deadline?
>>> what's the consideration?
>> I also thought it was silly to have different behaviours, so I tried
>> the following patch that makes deadline use sync/async instead of
>> read/write.  All the benchmarks I tried showed that performance
>> dropped or remained constant at best, so I didn't propose it.
>> Maybe you will have more luck...
> Hello,
> Which benchmark tool do you use? I'd like to have a try. I think the
> I/O behavior is an important factor which can affect the performance.

I can't find the original results, but from memory I tried FIO (many
random readers with various I/O sizes), postmark, and compilebench
on a single-disk and 10-disk hardware RAID system.


    -- Aaron
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